Method of making dental crowns



- Nov. 26, 1929. J PETRY 1,737,172

I IIYL I I METHOD OF MAKING DENTAL cnowns Original Filed April 8. 1927 2 Sheets-Sheet 1 Nov. 26, 1929. J. PETRY METHOD OF MAKING DENTAL CROWNS Original Filed April 8. 1927 2 Sheets-Shee 2 INVENTOR Patented Nov. 26, 1929 UNITED STATES JACOB ,PETRY, OF PITTSBURGH, PENNSYLVANIA METHOD OF MAKING DENTAL CROWNS Original application filed April 8, 1927, Serial No. 181,982. Divided and this application filed April 23, 1929.

Serial No. 357,413.

My invention relates particularly to tooth crowns such as are employed in dentistry, and this application constitutes a division of my application Serial No. 181,982, filed April My invention has for its object the provision of an improved method of making tooth crowns, whereby a better fitting crown is obtained and one which is free from various imperfections heretofore commonly present in tooth crowns.

Various other objects and advantages of the invention will be apparent from the following discussion, and are discussed more in 1 detail in my said application.

In the accompanying drawing, I have shown one means for practising my inven tion; Fig. 1 is a schematic View showing the manner in which a crown blank may be passed through the early stages of formation; Fig. 2 is an elevational sectional view .of apparatus by means of which the cutting edge of the crown maybe given its'prelimi nary or partial. form; Fig. 3 is a vertical sectional view of the crown blank following shaping thereof by the apparatus of Fig. 2; Fig. 4 is a view taken on the line IV-IV of Fig. 3; Fig. 5 is a plan view of the structure wherein the final forming operation is performed on the crown; Fig. 6 is a view of a portion of the apparatus of Fig. 5, but-showing the lateral dies in closed position; Fig. 7 is an elevational sectional view of the die structure of Fig. 6, but showing the fluidpressure crown expanding apparatus in operative relation thereto; Fig. 8 is a vertical sectional view of the crown after its removal from the die Fig. 9 is a view taken on the line IXIX of Fig. 8: Fig. 10 shows views taken on-the line XX of Fig. 9 before and after compression on the line Z)Z), and Fig.

11 is a view showing two completed crowns. In Fig. 1 of the drawing, I show a die block or plate 12 that is provided with a number of holes with which plungers 13, 14,

15 and 16 co-operate. The plungers are shown as mounted on a vertically reciprocable head 17 that may be operated in any desired manner to move the plungers into the plate In making tooth crowns, a disc 18 ofgold or other suitable metal is placed in the position shown, and the plunger head 17 brought down to depress said disc. The partially-formed cartridge is then moved into the next smaller hole and its diameter reduced by the plunger 22. In the drawing, I have shown four plungers of progressively smaller cross sectional area, and each tending toward an oval form in cross section; the plunger 16 being somewhat more oval than the plungers 14 and 15. A greater or less number of plungers may be provided.

After the crown has been operated upon by the plungers, it'is placed in a die block 19 that may be of fibrous or other relatively soft material, so that the crown will not be injured when a tool 20 is brought into position to shape the crown blank within the die 19. The tool 20 is somewhatedged at its lower end so asto give the blank 21 approximately the shape shown in Figs. 3 and l.

It will beseen that the crown at this stage has its occlusal or cutting surface partially formed, but the portions a thereof are rounded, instead of being approximately angular, as in the case of front teeth. This procedure is necessary, since if the corners of the tool 20 were angular enough to give the cutting edge of the crown its final form, they would tend to cut or tear through the metal of In order to fill out the lower corners w-a of the crown to render them approximately angular as shown in Fig. 11, so that there will be no space between adjacent crowns for the entry of food and to give-them a natural tooth form, I compress the'lower. end-of the crown between suitable dies on the line b-?; (Fig. 10) which action displaces the crown metal in such manner as to reduce the depth of the crown on the line 6-?) and thereby effects the filling out of the corners a to change them from the contours of Fig. i to the contours of Fig. 9, but produces a sharpened cutting edge similar to that possessed by front teeth. It will thus be seen that the additional metal required for producing the properly-shaped corners a is secured through displacement of surplus metal from other portions of the crown, instead of by merely thinning or stretching of the metal at the corners as would be the case if a punch weredepended upon to fill out such corners. This is highly important because the biting edge and its corners are subjected to great wear and any thinning of the metal is of course undesirable. The sides or vertical edges of the crown are then compressed as on the line 0.@ (Fig. 9) to change. the upper portion thereof from the contour of Fig. 4 to the contour of Fig. 9, and render it approximately of natural front tooth formation.

Instead 'of depending upon the compression of the'closed end of the crown to fill out at the corners aa, I may compress the crown slightly on the line a2x of Fig. 9, and in this manner also providing for sharpened or angular corners at a-a, without stretching of the metal by a plunger die. The compression on the line ww would of course not be so great-as 011 the line cc, since the sides or edgesof the crown'must taper upwardly in order to have the upper or gingeval portion of the crown of more nearly circular form than the lower portion thereof, as in the case of a natural tooth. V

After the crown has been given the contour shown in Figs. 8 and 9, I introduce it into fluid pressure dies, so that it may be given the slight further expansion which may be necessary in order to remove any irregularities that may be'present, and to bring it more accurately to the shape of a natural tooth, including protuberances or depressions which may be found in natural teeth. This final shaping of the crown is effected by means of fluid pressure introduced into the crown through a pressure head 23 that is brought into engagement with the upper sides of lateral dies 24;'and 25. A bottom'die 26 is recessed to receive the occlusal end of the crown 21, while the lateraldies 24 and 25 are of somewhat approximately semi-circular or semi-oval form. I w r The lateral die 24: is slidably mounted upon a block 27 and is movable toward and from the die25 bymeans of a lever 28, which is pivoted at 29 to the block 27. A link 30r con- Upon insertion of the crown 21 and the closure of the dies 24 and 25 as shown in Fig. 6, the pressure head 23 is brought into op erative position as shown in Fig. 7, and fluid pressure admitted to effect final shaping of the crown. The die may then be opened and the crown removed, at which time it will have approximately its final shape.

I claim as my invention 1. The method of forming flat or front dental crowns, which comprises forcing an elliptical cartridge through progressively smaller perforations, by a series of plungers that are successively of smaller diameter in one direction and each more closely conforming to the cross sectional contour of a front tooth, to thereby gradually diminish the smaller diameter of the crown, and thereafter compressing the closed end of the cartridge on its smaller diameter to increase the sharpness of the cutting edge, and expanding the cartridge, by fluid pressure, within a die having the contour of finished crown.

2. The method of forming flat or front dental crowns, which comprises forcing an elliptical cartridge through progressively smaller perforations, by a series of plungers that are successively of smallerdiameter in one direction and each more closeiy conforming to the cross sectional contour of a front tooth, to thereby gradually diminish the smaller diameter of the crown, and thereafter completing the shaping of the crown, by injecting fluid under pressure into the crown while it is confined in a die, to give it the contour of a natural front tooth. I

3. The method of forming flat or front dental crowns, which comprises forcing an elliptical cartridge through progressivelv smaller perforations, by a series of plungers that are successively of smaller diameter in one direction and each more closely conforming to the cross sectional contour of a front tooth, to thereby gradually diminish the smaller'diameter of the crown, compressing the closed end of the cartridge on its smaller diameter to increase the length and sharpness of the cutting edge, compressing the cartridge on its longer diameter at its open end, and expanding the cartridge by fluid pressure, within a die, to give it the natural contour of a tooth.

In testimony whereof I, the said JAoon PETRY have hereunto set my hand.

JACOBPETRY.

nects the lever 28 with the die 24, so thatupon oscillation of such lever, the die 24: will be I moved toward and from the. die 25.. 

